Upload picture

Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?

Goes well beyond the annotations (readOnlyHint=false, destructiveHint=false, openWorldHint=true, idempotentHint=false). It discloses upload acceptance rules (real JPEG/PNG/WEBP, <=10 MB, absolute path, everything else refused), the side effect that a picture gets a publicly reachable CDN URL even before being attached to an item, and that nothing is transmitted unless confirm=true.

Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.

Is the description appropriately sized, front-loaded, and free of redundancy?

Front-loads the core action and return, then constraints, then the confirm workflow in a logical sequence. Four sentences, each carrying distinct information, with no filler or repetition.

Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.

Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?

With no output schema, the description still states what comes back (picture id, public CDN URL). File validation limits, the confirm gate, and the workflow are all covered, so an agent has everything needed to call this correctly on the first try.

Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?

Schema description coverage is 100%, so the baseline is 3, but the description adds genuine intent for confirm (preview vs. actual upload) and the human-approval gate that the schema field description only states mechanically. It does not add format detail for file_path beyond the schema's own note.

Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

Does the description clearly state what the tool does and how it differs from similar tools?

States a specific verb and resource ('Upload a local image to Mercado Livre') plus the return value ('return its picture id'). It is unambiguously distinct from every sibling, none of which are upload tools, and pairs naturally with ml_update_item.

Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

Does the description explain when to use this tool, when not to, or what alternatives exist?

Gives an explicit operating procedure: call without confirm to get a preview, show the preview to the user, then call again with confirm=true only after explicit approval. It also names the downstream step (attaching via ml_update_item), so the when and the how are both pinned down.

Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.